Image reading apparatus such as a copier, facsimile, and image scanner are typically provided with a feed mechanism that feeds the object of read or workpiece, typically coming in the form of a sheet material such as a sheet of paper, in the forward and rearward direction. Such image reading apparatuses are further typically provided with a holder for holding the sheet of read object which comprises a holder base and a transparent holder cover. The image of the read object is obtained by reading the surface of the read object with an image scanner while feeding the holder clamping the read object in the forward and rearward direction.
The image scanner is typically configured by components such as a light source, lens, and a plurality of imaging devices. One of the problems encountered in such image scanners is the unevenness in the level of concentration of the read image which may be caused by the variation in the properties of the imaging devices, variation in the brightness of the light source, and the aberration of the lens. Thus, the read image is subjected to a shading correction to correct the concentration level. The shading correction typically involves reading a reference member including, for example, a white reference color with the image scanner prior to the reading of the read object, generating correction data based on the image data of the read reference member, and applying the correction data to correct the concentration level of the read object.
A reference member for shading correction is typically provided on the leading head of the holder being fed into the image reading apparatus. In order to obtain white reference information, the reference member is formed in a white color exhibiting a high level of brightness. By reading the reference member with the image scanner during the image reading, the latest correction data is always available to enable execution of appropriate shading correction.
A cutting apparatus is known that cuts a workpiece made of materials such as paper and cloth in the desired shape. The workpiece is held by a holding member during the cutting operation. By providing an image sensor serving as an image reading unit on such cutting apparatus, information such as the location, size, and the outline of the workpiece held by the holding member may be detected while also enabling reading of the original image of the workpiece for generation of cut data.
The above described application also requires shading correction of the read object in order to obtain a good read image. Thus, a reference member for shading correction, similar to the foregoing may be provided on the holding member. However, the reference member, when provided on the holding member, may be contaminated by the debris resulting from the cutting of the workpiece. Further, scratches resulting from the repeated cutting accumulate on the surface of the holding member. Thus, the holding member is considered as a consumable which is replaced by a new one after being used for approximately ten times. In this respect, the provision of the reference member brings up the cost of the overall system.